The Astrophysical Journal最新文献_第3页

Electron Acceleration in Thinning Nonreconnecting Current Sheets in a Quasi-parallel Shock 准平行激波中非重新连接电流片变薄的电子加速

The Astrophysical Journal Pub Date : 2025-10-13 DOI: 10.3847/1538-4357/ae0327

N. Bessho, L.-J. Chen, M. Hesse, J. Ng, L. B. Wilson and J. E. Stawarz

{"title":"Electron Acceleration in Thinning Nonreconnecting Current Sheets in a Quasi-parallel Shock","authors":"N. Bessho, L.-J. Chen, M. Hesse, J. Ng, L. B. Wilson and J. E. Stawarz","doi":"10.3847/1538-4357/ae0327","DOIUrl":"https://doi.org/10.3847/1538-4357/ae0327","url":null,"abstract":"We study electron energization in turbulence-generated current sheets in the shock transition region by means of fully kinetic collisionless plasma simulations and theory. Using parameters in the Earth’s bow shock, we perform a two-dimensional particle-in-cell simulation of a quasi-parallel shock. In shock turbulence, many current sheets are produced, including those exhibiting magnetic reconnection and those that are not reconnecting. The electron temperature is enhanced in nonreconnecting current sheets as well as in reconnecting current sheets and magnetic islands. Performing electron trajectory tracing analysis, we find that energetic electrons are produced in nonreconnecting thinning current sheets. The motional electric field during the thinning process of a current sheet energizes both magnetized and unmagnetized electrons. We analytically show that the energization rate for unmagnetized electrons is slightly less than that of adiabatic energization for magnetized electrons, but unmagnetized electrons can be effectively trapped in magnetic field structures formed in thinning current sheets and continue to be energized. These nonreconnecting current sheets produce energetic electrons whose energies are comparable to the energetic electrons produced in magnetic islands, and they can reach the injection energy for diffusive shock acceleration, which is an acceleration mechanism for producing cosmic rays. The number of electrons that are energized in nonreconnecting current sheets is about a quarter of that in reconnection regions. The energization mechanism can be applicable to various space and astrophysical environments, including planetary bow shocks and supernova remnant shocks.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"40 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145282894","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

The Response of Warm Absorbers to the Variations in the Ionizing Continuum in the Active Galaxy NGC 4051 活动星系ngc4051中热吸收体对电离连续谱变化的响应

The Astrophysical Journal Pub Date : 2025-10-13 DOI: 10.3847/1538-4357/ae032f

Dev R. Sadaula, Timothy R. Kallman and Sibasish Laha

{"title":"The Response of Warm Absorbers to the Variations in the Ionizing Continuum in the Active Galaxy NGC 4051","authors":"Dev R. Sadaula, Timothy R. Kallman and Sibasish Laha","doi":"10.3847/1538-4357/ae032f","DOIUrl":"https://doi.org/10.3847/1538-4357/ae032f","url":null,"abstract":"We present a time-resolved X-ray spectral analysis of the warm absorbers in the Seyfert galaxy NGC 4051, which has an active galactic nucleus (AGN), using observations from the Neutron Star Interior Composition Explorer (NICER). Despite NICER’s moderate spectral resolution, its high-cadence monitoring allows us to probe the response of the ionized outflows, also known as warm absorbers, on timescales of ∼5500 s. We detect two distinct components of ionized absorbers in this source. The variability in the ionization parameter of the low-ionization warm absorber component, which tracks changes in the ionizing flux with no measurable time lag. This rapid response implies photoionization equilibrium and places a lower limit on the electron density of ≳9 × 106 cm−3 based on the most abundant ionic species, O VII. The absorber is located within ∼0.02 pc of the central source, consistent with an origin in the inner regions of the active nucleus. In contrast, the high-ionization absorber remains consistently under-ionized relative to equilibrium predictions. This suggests that it may be the collisional plasma, which was also detected in this source in the previous studies. These results demonstrate that time-resolved spectroscopy, even with moderate-resolution instruments, can provide valuable constraints on the density and location of warm absorbers in AGN. As a potential candidate source of AGN feedback, the study of these ionized outflows is crucial in understanding AGN–host galaxy interactions.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"124 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145282895","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

New TeV-emitting BL Lac Candidates from the eROSITA X-Ray Survey 来自eROSITA x射线调查的新tev发射BL Lac候选者

The Astrophysical Journal Pub Date : 2025-10-13 DOI: 10.3847/1538-4357/adff87

Cassidy Metzger, Andrea Gokus and Manel Errando

{"title":"New TeV-emitting BL Lac Candidates from the eROSITA X-Ray Survey","authors":"Cassidy Metzger, Andrea Gokus and Manel Errando","doi":"10.3847/1538-4357/adff87","DOIUrl":"https://doi.org/10.3847/1538-4357/adff87","url":null,"abstract":"TeV-emitting BL Lac–type blazars represent the extreme end of the blazar population. They are characterized by relatively weak jets and radiatively inefficient accretion disks. Particles accelerated in these jets experience fewer radiative losses, allowing them to reach energies beyond the TeV scale and produce TeV gamma-ray emission. The study of TeV blazars is constrained by the limited number of known sources in this category. Currently, only 56 high-synchrotron-peaked BL Lacs have been detected at energies above 0.1 TeV. Searches for TeV emission from BL Lacs typically target sources with bright X-ray emission and a synchrotron peak at or above 1 keV. The recently released eRASS1 catalog by the eROSITA collaboration, which covers half of the sky, represents the deepest X-ray survey in the soft X-ray band to date. Utilizing the eROSITA survey, combined with infrared data from the Wide-field Infrared Survey Explorer and archival radio observations, we have identified 121 TeV-emitting blazar candidates. Our search introduces selection criteria based on the radio to infrared that remove quasar-like objects that have similar infrared spectra and X-ray fluxes as TeV-emitting BL Lacs. In our search, we find 23 objects that had not been detected in the ROSAT X-ray survey and 11 that have not been previously associated with blazars. The candidates resulting from our search are suitable for follow-up observations with currently operating imaging atmospheric Cherenkov telescopes, as well as future facilities like the CTAO Observatory.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"94 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145282891","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Low-latitude Sunspot Group Tilt Angles in 15–24 Activity Cycles 低纬度太阳黑子群在15-24个活动周期内的倾角

The Astrophysical Journal Pub Date : 2025-10-13 DOI: 10.3847/1538-4357/ae09a7

Andrey G. Tlatov

引用次数: 0

Transport of Mirror Mode Structures through Saturn’s Magnetopause Reconnection 通过土星磁层顶重联的镜面结构输运

The Astrophysical Journal Pub Date : 2025-10-12 DOI: 10.3847/1538-4357/ae08af

S. B. Xu, S. Y. Huang, Z. G. Yuan, K. Jiang, H. H. Wu, J. Zhang, Z. Wang, Q. Y. Xiong and R. T. Lin

引用次数: 0

Reexamining the Power-law Relationship between Global Solar X-Ray Luminosity and Total Unsigned Magnetic Flux 太阳x射线总光度与总无符号磁通量幂律关系的再检验

The Astrophysical Journal Pub Date : 2025-10-12 DOI: 10.3847/1538-4357/ae0a54

Keiji Yoshimura, Aki Takeda and Dana W. Longcope

{"title":"Reexamining the Power-law Relationship between Global Solar X-Ray Luminosity and Total Unsigned Magnetic Flux","authors":"Keiji Yoshimura, Aki Takeda and Dana W. Longcope","doi":"10.3847/1538-4357/ae0a54","DOIUrl":"https://doi.org/10.3847/1538-4357/ae0a54","url":null,"abstract":"The mechanism heating the solar corona remains unclear but is generally hypothesized to involve magnetic fields. One probe of this hypothesis is a statistical study relating coronal emission to magnetic flux. A. A. Pevtsov et al. conducted such a survey relating X-ray luminosity (LX) to unsigned photospheric magnetic flux (Φm) for a variety of heated plasmas, ranging from solar quiet regions to T Tauri stars. They reported that a power-law relationship, , described the entire collection but found that the subset from solar disk–integrated flux was better fit by a broken power law. Several parameters entering the calculations of LX and Φm have the potential to impact this analysis. The present study uses more recent data to reanalyze the flux–luminosity relationship for the full solar disk and examines its dependence on parameters. We find the most significant effects from two parameters: the cutoff field strength used in computation of Φm and the range of wavelengths defining LX. We find further that lower choices of cutoff yield a broken power law, while an optimal choice yields a single power law and minimizes the fitting residual. The critical cutoff is well above the magnetogram noise level, suggesting that weaker fields may not contribute significantly to the X-ray corona. We also find that LX defined by decreasing wavelength ranges requires an increasing critical cutoff. The resulting power-law indices vary, but all fall around 1.2.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"116 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145277440","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Vibrational Spectroscopy of C 60 ... c60的振动光谱…

The Astrophysical Journal Pub Date : 2025-10-12 DOI: 10.3847/1538-4357/adf6de

Thomas E. Douglas-Walker, Olivia O’Neill and Ewen K. Campbell

引用次数: 0

Evolution of Large-scale Structures in the Energetic Neutral Atom Sky Maps in Energy and Solar Activity 能量和太阳活动中高能中性原子大尺度结构的演化

The Astrophysical Journal Pub Date : 2025-10-12 DOI: 10.3847/1538-4357/adfa24

Justyna M. Sokół, Jonathan Gasser, Merav Opher, Marc Kornbleuth, Kostas Dialynas, André Galli, Maher A. Dayeh, Stephen A. Fuselier, Daniel B. Reisenfeld and Herbert O. Funsten

{"title":"Evolution of Large-scale Structures in the Energetic Neutral Atom Sky Maps in Energy and Solar Activity","authors":"Justyna M. Sokół, Jonathan Gasser, Merav Opher, Marc Kornbleuth, Kostas Dialynas, André Galli, Maher A. Dayeh, Stephen A. Fuselier, Daniel B. Reisenfeld and Herbert O. Funsten","doi":"10.3847/1538-4357/adfa24","DOIUrl":"https://doi.org/10.3847/1538-4357/adfa24","url":null,"abstract":"The heliospheric energetic neutral atoms (ENAs) are products of charge exchange between solar wind and pick-up ions and interstellar neutral atoms. They are created in different regions of the heliosphere and its boundary region with the interstellar medium, constituting different ENA populations, and they carry information about their parent populations and production processes. Thus, ENAs enable mapping of the global structure of the heliosphere and the processes within and at its edge. Three instruments have provided sky maps of the heliospheric ENAs from 200 eV up to 44 keV over the solar activity cycle. The IBEX-Lo and IBEX-Hi instruments on board the Interstellar Boundary Explorer (IBEX) have provided ENA sky maps from 200 eV to 4.3 keV (central energy) from 2009 throughout Solar Cycle 24. The Ion and Neutral Camera (INCA) on board the Cassini–Huygens mission provided sky maps of the ENAs from 8–44 keV (central energy) on the spacecraft route to and in orbit around Saturn through Solar Cycles 23 and 24. We compare large-scale structures of ENA enhancements present across the sky maps in a wide energy range based on IBEX-Lo, IBEX-Hi, and INCA. They include Ribbon, heliotail lobes, and upwind ENA enhancement. We report on similarities and differences observed, including the evolution of the Ribbon from low to higher energies, and the presence of confined north and south heliotail lobes up to 44 keV.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"70 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145277441","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Multifidelity Emulator for Large-scale 21 cm Lightcone Images: A Few-shot Transfer Learning Approach with Generative Adversarial Network 大规模21厘米光锥图像的多保真仿真：一种基于生成对抗网络的少镜头迁移学习方法

The Astrophysical Journal Pub Date : 2025-10-12 DOI: 10.3847/1538-4357/ae0325

Kangning Diao and Yi Mao

{"title":"Multifidelity Emulator for Large-scale 21 cm Lightcone Images: A Few-shot Transfer Learning Approach with Generative Adversarial Network","authors":"Kangning Diao and Yi Mao","doi":"10.3847/1538-4357/ae0325","DOIUrl":"https://doi.org/10.3847/1538-4357/ae0325","url":null,"abstract":"Emulators using machine learning techniques have emerged to efficiently generate mock data matching the large survey volume for upcoming experiments, as an alternative approach to large-scale numerical simulations. However, high-fidelity emulators have become computationally expensive as the simulation volume grows to hundreds of megaparsecs. Here, we present a multifidelity emulation of large-scale 21 cm lightcone images from the epoch of reionization, which is realized by applying the few-shot transfer learning to training generative adversarial networks (GAN) from small-scale to large-scale simulations. Specifically, a GAN emulator is first trained with a huge number of small-scale simulations, and then transfer-learned with only a limited number of large-scale simulations, to emulate large-scale 21 cm lightcone images. We test the precision of our transfer-learned GAN emulator in terms of representative statistics including global 21 cm brightness temperature history, 2D power spectrum, and scattering transform coefficients. We demonstrate that the lightcone images generated by the transfer-learned GAN emulator can reach the percentage level precision in most cases on small scales, and the error on large scales only increases mildly to the level of a few tens of percent. Nevertheless, our multifidelity emulation technique saves a significant portion of computational resources that are mostly consumed for generating training samples for GAN. On estimate, the computational resource by training GAN completely with large-scale simulations would be 1 to 2 orders of magnitude larger than using our multifidelity technique. This implies that our technique allows for emulating high-fidelity, traditionally computationally prohibitive, images in an economic manner.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"124 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145277449","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Impulsive Mixing of Stellar Populations in Dwarf Spheroidal Galaxies 矮球状星系中恒星群的脉冲混合

The Astrophysical Journal Pub Date : 2025-10-12 DOI: 10.3847/1538-4357/adfa27

Raphaël Errani, Matthew G. Walker, Simon Rozier, Jorge Peñarrubia and Julio F. Navarro

{"title":"Impulsive Mixing of Stellar Populations in Dwarf Spheroidal Galaxies","authors":"Raphaël Errani, Matthew G. Walker, Simon Rozier, Jorge Peñarrubia and Julio F. Navarro","doi":"10.3847/1538-4357/adfa27","DOIUrl":"https://doi.org/10.3847/1538-4357/adfa27","url":null,"abstract":"We study the response of mono-energetic stellar populations with initially isotropic kinematics to impulsive and adiabatic changes to an underlying dark matter potential. Half-light radii expand and velocity dispersions decrease as enclosed dark matter is removed. The details of this expansion and cooling depend on the timescale on which the underlying potential changes. In the adiabatic regime, the product of half-light radius and average velocity dispersion is conserved. We show that the stellar populations maintain centrally isotropic kinematics throughout their adiabatic evolution, and their densities can be approximated by a family of analytical radial profiles. Metallicity gradients within the galaxy flatten as dark matter is slowly removed. In the case of strong impulsive perturbations, stellar populations develop power-law-like density tails with radially biased kinematics. We show that the distribution of stellar binding energies within the dark matter halo substantially widens after an impulsive perturbation, no matter the sign of the perturbation. This allows initially energetically separated stellar populations to mix, to the extent that previously chemo-dynamically distinct populations may masquerade as a single population with large metallicity and energy spread. Finally, we show that in response to an impulsive perturbation, stellar populations that are deeply embedded in cored dark matter halos undergo a series of damped oscillations before reaching a virialized equilibrium state, driven by inefficient phase mixing in the harmonic potentials of cored halos. This slow return to equilibrium adds substantial systematic uncertainty to dynamical masses estimated from Jeans modeling or the virial theorem.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"39 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145277434","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0